This is so random.
Usually if one sings a cover there's some current relevance to it or it's a live collabo on the show.
I hope she gets to sing one song of herself as well, it's her 20th Anni after all.
Even aiko is singing a medley because of her anniversary.

And now I've just read that day 1, where Ayu is performing, will be a "formal setting" while day 2 will be the "informal" one. The song choice makes even less sense now. xD